Computerscience

PROJECTS REQUIREMENT

The purpose of this project exercise is to build a digital thermometer that will be able to display the measured temperatures in both degrees Celsius and degrees Fahrenheit. In this project I decide to use LM35 temperature sensor to sense the temperature of the surrounding. The output of the sensor is a small voltage that is in the range of millivolts. This small voltage will be amplified to measurable levels using operational amplifiers. Op-amp adders and other mathematical amplifiers will be used to convert the temperature from degrees Celsius to degrees Fahrenheit. The two voltage levels for the temperature in degrees Celsius and degrees Fahrenheit are to measured and displayed on multi-meters to check on the proper operation of the circuit. The circuit is to be first built on simulation software (MULTISIM) and then later on a breadboard. The components to be used in the project are expected to be locally available.

BLOCK DIAGRAM

The functional block diagram of this project is as shown in the figure below:

Display 2 ( for temperature in degrees Fahrenheit)

Amplifier 3

Display 1 (for

Temperature in degrees Celsius)

Amplifier 2

Amplifier 1

Temperature

Sensor (LM35)

The function of the various sub-blocks is described as follows:

1. Temperature sensor

In this project exercise I will be using the LM35 temperature sensor. The LM35 is a precision IC temperature sensor whose output is proportional to the temperature (in ◦C). The sensor has an operating temperature range from -55°C to 150°C. The output of the sensor varies by 10mV in every oC rise/fall.

1. Amplifier 1

The output of the sensor is in the range of millivolts. This voltage need to be amplified into measurable levels. An amplifier is necessary for this stage. Inn this stage an inverting amplifier with a sufficient gain will be used.

1. Amplifier 2

The output of the amplifier in the previous stage is inverted or negative. Another inverting amplifier is necessary to convert back the voltage from negative to positive.

1. Amplifier 3

This is a mathematical amplifier that will perform the conversion from degrees Celsius to degrees Fahrenheit.

1. Display 1

This block will display the temperature in degrees Celsius

1. Display 2

This block will help to display the temperature in degrees fahrenheit